Optical deflector, and optical scanning device and image forming apparatus equipped with same

Abstract

Disclosed is an optical deflector which includes: a polygonal mirror, a drive motor, a cover member, and a temperature detection unit. The cover member includes: a first cover portion defining a first space in which the polygonal mirror is installed, wherein the first cover portion is formed with a first opening opened in opposed relation to an outer peripheral surface of the polygonal mirror; a second cover portion defining a second space which is communicated with the first space and in which the drive motor is installed, wherein the second cover portion is formed with a second opening opened in opposed relation to a motor body of the drive motor; and a third cover portion defining a third space which is communicated with the second space. The temperature detection unit is mounted to the third cover portion so as to close the third space.

The invention claimed is: 
     
       1. An optical deflector comprising:
 a drive motor including a motor body and a rotary shaft protruding from the motor body; 
 a polygonal mirror provided on one end of the rotary shaft located on one side in an axial direction of the rotary shaft, in an integrally rotatable manner, and having an outer peripheral surface to be irradiated with light, wherein the polygonal mirror deflects light irradiating the outer peripheral surface thereof in such a manner as to enable the deflected light to be scanned with respect to a given irradiation target member, while being rotated about the rotary shaft; 
 a cover member covering the polygonal mirror and the drive motor; and 
 a temperature detection unit which detects an internal temperature of the cover member, 
 wherein the cover member includes:
 a first cover portion covering the polygonal mirror from the one side in the axial direction to thereby define a first space in which the polygonal mirror is installed, the first cover portion being formed with a first opening opened in opposed relation to the outer peripheral surface of the polygonal mirror; 
 a second cover portion disposed on the other side opposite to the one side in the axial direction, with respect to the first cover portion, to define a second space which is communicated with the first space and in which the drive motor is installed, the second cover portion being formed with a second opening opened in opposed relation to the motor body; and 
 
 a third cover portion defining a third space which is communicated with the second space, 
 and wherein the temperature detection unit is mounted to the third cover portion in such a manner as to close the third space. 
 
     
     
       2. The optical deflector as recited in  claim 1 , wherein the second cover portion comprises:
 a first extension section extending from the first cover portion toward one side in a first direction orthogonal to the axial direction; and 
 a second extension section extending from the first cover portion in a second direction orthogonal to both of the axial direction and the first direction, 
 and wherein 
 the second opening is formed to extend across the first extension section and the second extension section, and 
 the third cover portion is disposed on the one side in the axial direction with respect to the first extension section of the second cover portion, in such a manner as to define the third space which is communicated with the second space. 
 
     
     
       3. The optical deflector as recited in  claim 2 , wherein
 the second extension section of the second cover portion includes a first sub-section extending from the first cover portion toward one side in the second direction, and a second sub-section extending from the first cover portion toward the other side opposite to the one side in the second direction, 
 and wherein: 
 the second opening is formed to extend across the first extension section and the first sub-section of the second extension section; 
 the second cover portion is formed with a third opening opened in opposed relation to the motor body, the third opening extending across the first extension section and the second sub-section of the second extension section; and 
 in plan view as viewed in the axial direction, the temperature detection unit is located between the second opening and the third opening. 
 
     
     
       4. The optical deflector as recited in  claim 2 , wherein:
 the first extension section of the second cover portion is formed with a fourth opening opened toward the one side in the axial direction; and 
 the third cover portion is formed in a tubular shape extending toward the one side in the axial direction, from a peripheral edge of the fourth opening to surround the fourth opening, the third cover portion having a fifth opening at an end thereof on the one side in the axial direction, and defining the third space which is communicated with the second space through the fourth opening. 
 
     
     
       5. The optical deflector as recited in  claim 1 , wherein the temperature detection unit includes a plate-shaped substrate having heat conductivity, and a temperature detection sensor attached to one principal surface of the substrate, the temperature detection unit being mounted to the third cover portion in such a manner that the temperature detection sensor is disposed inside the third space. 
     
     
       6. An optical scanning device comprising:
 the optical deflector as recited in  claim 1 ; 
 a light source which emits light toward the outer peripheral surface of the polygonal mirror; and 
 a correction section which corrects positional deviation in scanning applied to the irradiation target member by the polygonal mirror, based on temperature data detected by the temperature detection unit. 
 
     
     
       7. The optical scanning device as recited in  claim 6  which further comprises:
 a light source control section which controls a light irradiation operation of the light source; 
 a rotational drive control section which controls a rotational drive operation of the drive motor for rotationally driving the polygonal mirror; and 
 a temperature detection control section which instructs the temperature detection unit to continuously perform a temperature detection operation, 
 wherein the correction section is configured to perform the positional deviation correction, based on temperature data detected in a given detection duration by the temperature detection unit under control of the temperature detection control section, 
 and wherein the detection duration includes a period of time between a first time point when a rotational speed of the polygonal mirror reaches a given value under control of the rotational drive control section, and a second time point just before start of the light irradiation operation of the light source under control of the light source control section. 
 
     
     
       8. An image forming apparatus comprising:
 the optical scanning device as recited in  claim 6 , and 
 an image carrying member serving as the irradiation target member which is to be scanned with light deflected by the polygonal mirror so as to form an electrostatic latent image on a surface thereof.